Image stabilization apparatus and method and image capturing apparatus

ABSTRACT

An image stabilization apparatus comprises a motion vector detector that detects a motion vector from images repeatedly output from an image sensor; a first calculator that calculates a first image stabilization coefficient based on the motion vector; a second calculator that calculates a second image stabilization coefficient based on acceleration of shake of an image capturing apparatus; a determination unit that selects either of the first or the second image stabilization coefficient based on information about accuracy of detection of the motion vector; and a translational shake calculator that calculates an amount of translational shake using the first or the second image stabilization coefficient selected by the determination unit. In a case where the information indicates that the accuracy is low, the determination unit selects the second image stabilization coefficient, and select the first image stabilization coefficient otherwise.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an image stabilization apparatus andmethod and image capturing apparatus and more particularly to an imagestabilization apparatus and method and image capturing apparatus thatperform translational image stabilization.

Description of the Related Art

In recent years, the number of cameras equipped with image stabilizationcontrol devices has been increasing in the market. In order to enableshooting of images without blurring even if camera shake occurs duringexposure, it is necessary to detect angular shake and translationalshake of the camera, and move the image stabilization unit according tothe detected values to cancel the shake.

In recent years, improvements in the performance of angular velocitysensors have made it possible to detect angular shake in a widerfrequency band than before, especially in a low frequency band.Therefore, the image stabilization performance with respect to theangular shake of the camera caused by camera shake has been improved. Onthe other hand, due to the improvement of the image stabilizationperformance with respect to the angular shake, the translational shakehas become conspicuous. As a method of translational imagestabilization, Japanese Patent No. 4789614 describes a technique inwhich the ratio of an output of an accelerometer to an output of anangular velocity meter is obtained as a radius of rotation, thetranslational shake is obtained from the radius of rotation and theoutput of the angular velocity meter, and the translational shake iscancelled by driving a correction unit.

However, due to the improvement in the performance of imagestabilization, even if the exposure period is long, it has becomepossible to take pictures with a camera being hand-held, which makes itnecessary to perform image stabilization in a lower frequency band. Animage signal is used in addition to a signal from the accelerometer inorder to perform image stabilization in a lower frequency band, and themethod of utilizing the image signal becomes an issue.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and performs translational image stabilization moreaccurately according to the conditions of the subject and the imagecapturing apparatus.

According to the present invention, provided is an image stabilizationapparatus comprising at least one processor and/or circuitry whichfunctions as: a motion vector detector that detects a motion vector fromimages repeatedly output from an image sensor; a first calculator thatcalculates a first image stabilization coefficient to be used forcalculating an amount of translational shake based on the motion vector;a second calculator that calculates a second image stabilizationcoefficient to be used for calculating an amount of translational shakebased on acceleration of shake of an image capturing apparatus; adetermination unit that selects either of the first image stabilizationcoefficient or the second image stabilization coefficient based oninformation about accuracy of detection of the motion vector by themotion vector detector; and a translational shake calculator thatcalculates an amount of translational shake using the first imagestabilization coefficient or the second image stabilization coefficientselected by the determination unit, wherein, in a case where theinformation indicates that the accuracy is low, the determination unitselects the second image stabilization coefficient, and select the firstimage stabilization coefficient otherwise.

Further, according to the present invention, provided is an imagestabilization apparatus comprising at least one processor and/orcircuitry which functions as: a first calculator that calculates animage stabilization coefficient to be used for calculating an amount oftranslational shake based on a motion vector obtained from imagesrepeatedly output from an image sensor; a gain unit that determines again based on a shutter speed at a time of shooting an image and ashooting distance; and a second calculator that calculates an amount oftranslational shake using the gain determined by the gain unit and theimage stabilization coefficient calculated by the first calculator,wherein the gain unit makes the gain larger in a case where the shutterspeed is a first shutter speed than in a case where the shutter speed isa second shutter speed which is faster than the first shutter speed, andwherein the gain unit makes the gain larger in a case where the shootingdistance is a first shooting distance than in a case where the shootingdistance is a second shooting distance which is longer than the firstshooting distance.

Furthermore, according to the present invention, provided is an imagecapturing apparatus comprising: an image sensor; and an imagestabilization apparatus that comprises at least one processor and/orcircuitry which functions as: a motion vector detector that detects amotion vector from images repeatedly output from the image sensor; afirst calculator that calculates a first image stabilization coefficientto be used for calculating an amount of translational shake based on themotion vector; a second calculator that calculates a second imagestabilization coefficient to be used for calculating an amount oftranslational shake based on acceleration of shake of an image capturingapparatus; a determination unit that selects either of the first imagestabilization coefficient or the second image stabilization coefficientbased on information about accuracy of detection of the motion vector bythe motion vector detector; and a translational shake calculator thatcalculates an amount of translational shake using the first imagestabilization coefficient or the second image stabilization coefficientselected by the determination unit, wherein, in a case where theinformation indicates that the accuracy is low, the determination unitselects the second image stabilization coefficient, and selects thefirst image stabilization coefficient otherwise.

Further, according to the present invention, provided is an imagecapturing apparatus comprising: an image sensor; and an imagestabilization apparatus that comprises at least one processor and/orcircuitry which functions as: a first calculator that calculates animage stabilization coefficient to be used for calculating an amount oftranslational shake based on a motion vector obtained from imagesrepeatedly output from an image sensor; a gain unit that determines again based on a shutter speed at a time of shooting an image and ashooting distance; and a second calculator that calculates an amount oftranslational shake using the gain determined by the gain unit and theimage stabilization coefficient found by the first calculator, whereinthe gain unit makes the gain larger in a case where the shutter speed isa first shutter speed than in a case where the shutter speed is a secondshutter speed which is faster than the first shutter speed, and whereinthe gain unit makes the gain larger in a case where the shootingdistance is a first shooting distance than in a case where the shootingdistance is a second shooting distance which is longer than the firstshooting distance.

Further, according to the present invention, provided is an imagestabilization method comprising: detecting a motion vector from imagesrepeatedly output from an image sensor; calculating a first imagestabilization coefficient to be used for calculating an amount oftranslational shake based on the motion vector; calculating a secondimage stabilization coefficient to be used for calculating an amount oftranslational shake based on acceleration of shake of an image capturingapparatus; selecting either of the first image stabilization coefficientor the second image stabilization coefficient based on information aboutaccuracy of detection of the motion vector; and calculating an amount oftranslational shake using selected one of the first image stabilizationcoefficient or the second image stabilization coefficient, wherein, thesecond image stabilization coefficient is selected in a case where theinformation indicates that the accuracy is low, and the first imagestabilization coefficient is selected otherwise.

Further, according to the present invention, provided is an imagestabilization method comprising: calculating an image stabilizationcoefficient to be used for calculating an amount of translational shakebased on a motion vector obtained from images repeatedly output from animage sensor; determining a gain based on a shutter speed at a time ofshooting an image and a shooting distance; and calculating an amount oftranslational shake using the gain and the image stabilizationcoefficient, wherein the gain is made larger in a case where the shutterspeed is a first shutter speed than in a case where the shutter speed isa second shutter speed which is faster than the first shutter speed, andwherein the gain is made larger in a case where the shooting distance isa first shooting distance than in a case where the shooting distance isa second shooting distance which is longer than the first shootingdistance.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the description, serve to explain the principles of theinvention.

FIG. 1A is a central sectional view of an image capturing apparatusaccording to a first embodiment of the present invention.

FIG. 1B is a block diagram showing a brief functional configuration ofthe image capturing apparatus according to the first embodiment.

FIG. 2 is a block diagram showing a configuration for calculating anamount of translational shake according to the first embodiment.

FIG. 3 is a diagram explaining an operation performed by a translationalshake extractor according to the first embodiment.

FIG. 4 is a flowchart showing a calculation process of an amount oftranslational shake according to the first embodiment.

FIG. 5 is a diagram showing an example of a table for determining a gainvalue according to a second embodiment.

FIG. 6 is a flowchart showing a calculation process of an amount oftranslational shake according to the second embodiment.

FIG. 7 is a block diagram showing a configuration for calculating anamount of translational shake according to a third embodiment.

FIG. 8 is a flowchart showing a calculation process of a firstcorrection coefficient according to the third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments will be described in detail with reference tothe attached drawings. Note, the following embodiments are not intendedto limit the scope of the claimed invention, and limitation is not madean invention that requires a combination of all features described inthe embodiments. Two or more of the multiple features described in theembodiments may be combined as appropriate. Furthermore, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

First Embodiment

FIGS. 1A and 1B are views showing an image capturing apparatus 1000equipped with an image stabilization control device according to thefirst embodiment, and specifically, FIG. 1A is a central cross-sectionalview of the image capturing apparatus 1000, and FIG. 1B is a blockdiagram which shows a functional configuration of the image capturingapparatus 1000.

As shown in FIG. 1A, the image capturing apparatus 1000 of the presentembodiment mainly includes a camera body 1 and a lens unit 2 that can beattached to and detached from the camera body 1. The camera body 1 andthe lens unit 2 are electrically connected via an electrical contact 11.It should be noted that the image capturing apparatus of the presentinvention is not limited to this configuration, and may be an imagecapturing apparatus in which a camera body and a lens unit areintegrally configured.

The lens unit 2 includes an imaging optical system 3 comprised of adiaphragm and a plurality of lenses including a focus lens, a zoom lensand an image stabilization lens 9 arranged on an optical axis 4, and alens system control unit 12. Further, the camera body 1 includes animage sensor 6, a rear display device 10 a, an electronic view finder(EVF) 10 b, an image stabilization unit 14, an angular velocity detector15, an acceleration detector 16, and a shutter mechanism 17.

In FIG. 1A, the z-axis is parallel to the optical axis 4. The x-axis andy-axis are orthogonal to the z-axis and parallel to sides of the imagesensor 6, respectively. In addition, in order to make the figure easierto see, the origin of the coordinate is written outside the imagecapturing apparatus 1000 in FIG. 1A, but the origin is actually locatedat the center of the image capturing apparatus 1000.

Further, as shown in FIG. 1B, the lens unit 2 further includes a lensactuator 13 for actuating the focus lens, the zoom lens, the imagestabilization lens 9, the diaphragm, and the like included in theimaging optical system 3. Further, the camera body 1 further includes acamera system control unit 5, a release detector 7, an operationdetector 8, a display unit 10, and a shutter actuator 18. The displayunit 10 includes the rear display device 10 a provided on the backsurface of the camera body 1 shown in FIG. 1A and the EVF 10 b providedin a finder of the camera body 1.

The release detector 7 detects an open/close signal of a release switch(not shown) that opens/closes in response to pressing of the releasebutton, and sends the detected open/close signal to the camera systemcontrol unit 5. The release detector 7 usually detects two types ofopen/close signals from a two-stage switch; one is the open/close signalfrom a switch that turns on when the release button is pressed halfway(hereinafter referred to as “SW1”) and the other is the open/closesignal of a switch that turns on when the release button is fullypressed (hereinafter referred to as “SW2”).

The operation detector 8 detects photographer's operations forinstructing, for example, shutter speed, F value, and mode setting.

Light from a subject passing through the imaging optical system 3 of thelens unit 2 is formed on an imaging surface of the image sensor 6 whilethe shutter mechanism 17 is open. The lens actuator 13 receives acontrol signal from the lens system control unit 12 and actuates theimaging optical system 3 so that a good image can be formed on the imagesensor 6. Further, the shutter mechanism 17 is controlled and actuatedby the shutter actuator 18 so that the exposure at the shutter speed setby the photographer or determined by the camera system control unit 5 isperformed. The image sensor 6 photoelectrically converts the incidentlight and outputs an electric signal (image signal) corresponding to anamount of light.

The camera system control unit 5 calculates a control amount for imagestabilization to reduce the effect of camera shake based on the signalsoutput from the release detector 7, operation detector 8, angularvelocity detector 15, and acceleration detector 16, and output thecontrol amount to the image stabilization unit 14 and the lens systemcontrol unit 12.

The lens system control unit 12 outputs a command based on the controlamount received from the camera system control unit 5 to the lensactuator 13. The lens actuator 13 actuates the image stabilization lens9 in the x and y directions of FIG. 1A, and performs image stabilizationthat takes into account both angular shake and translational shake.

On the other hand, the image stabilization unit 14 actuates the imagesensor 6 based on the control amount received from the camera systemcontrol unit 5. The image stabilization unit 14 actuates the imagesensor 6 in the x-direction and the y-direction of FIG. 1A, therebyperforms image stabilization that takes into account both angular shakeand translational shake. In addition, the image stabilization unit 14rotationally actuates the image sensor 6 around the z-axis to performimage stabilization that takes into account both angular shake andtranslational shake caused by rotational movement around the z-axis.

The correction method based on the control amount received from thecamera system control unit 5 is not limited to this, and other methodsmay be used. For example, so-called electronic image stabilization,which stabilizes an image by shifting the cropping position of an imageoutput from the image sensor 6, may be used, and the electronic imagestabilization and the image stabilization that actuates the image sensor6 described above may be used in combination as appropriate.

Image plane shake occurs in the image sensor 6 when the shake occurs inthe image capturing apparatus 1000. Hereinafter, the image plane shakeof the image sensor 6 due to translational shake is referred to as“image plane translational shake”, and the image plane shake of theimage sensor 6 due to angular shake is referred to as “image planeangular shake”.

FIG. 2 is a block diagram showing a configuration for calculatingtranslational shake, the angular velocity detector 15 and theacceleration detector 16 in the camera system control unit 5.

A motion vector detector 201 detects the moving velocity of a featurepoint from the movement amount of the feature points in images betweenframes, thereby detecting velocities of the image plane shake of theimage sensor 6 in the x-axis direction, the y-axis direction, and thez-axis direction of FIG. 1A. When the subject is not moving, the movingvelocity of the feature point represents the velocity of the image planeshake generated by the shake of the image capturing apparatus. When thesubject is moving, the moving velocity of the feature point representsthe sum of the velocity of the image plane shake generated by the shakeof the image capturing apparatus and the moving velocity of the subject.

Further, the velocity of the image plane shake detected by the motionvector detector 201 includes an image plane velocity of angular shakeand an image plane velocity of translational shake. The image planevelocity of angular shake is the velocity of the shake exerted on theimage plane by the image plane angular shake, and the image planevelocity of translational shake is the velocity of the shake exerted onthe image plane by the image plane translational shake.

The image stabilization amount detector 208 detects and outputs theimage plane velocity of the remnant of angular shake reduced by the lensactuator 13 and the image stabilization unit 14.

The angular velocity detector 15 detects the angular velocities aroundthe x-axis, y-axis, and z-axis of the coordinate axes shown in FIG. 1A,and outputs angular velocity signals. An angular velocity calculator 204calculates the image plane velocities of the angular shake bymultiplying the angular velocity signals output from the angularvelocity detector 15 by the focal length, and outputs the calculatedimage plane velocities of the angular shake.

A translational shake extractor 207 uses the output of the motion vectordetector 201, the output of the image stabilization amount detector 208,and the output of the angle velocity calculator 204 to calculate theimage plane velocity of translational shake and the image plane velocityof the remnant of the angular shake which has been reduced. Here, amethod of calculating the image plane velocity of translational shakeand the image plane velocity of the remnant of the angular shake whichhas been reduced will be described with reference to FIG. 3.

FIG. 3 is a conceptual diagram of an operation performed by thetranslational shake extractor 207. The sum of an image plane velocity ofangular shake (after reduction) 301, an image plane velocity of angularshake (before reduction) 302, and an image plane velocity oftranslational shake (before reduction) 303 shown in FIG. 3 correspondsto the velocity of the image plane shake that appears on the image planeof the image sensor 6 when no image stabilization operation isperformed.

The image plane velocity of angular shake (after reduction) 301 is theoutput of the image stabilization amount detector 208. The output of theangular velocity calculator 204 corresponds to the sum of the imageplane velocity of angular shake (after reduction) 301 and the imageplane velocity of angular shake (before reduction) 302. Therefore, theimage plane velocity of angular shake (before reduction) 302 can beobtained by subtracting the output of the image stabilization amountdetector 208 from the output of the angular velocity calculator 204.

Further, the output of the motion vector detector 201 corresponds to thesum of the image plane velocity of angular shake (before reduction) 302and the image plane velocity of translational shake (before reduction)303. Therefore, the image plane velocity of translational shake (beforereduction) 303 can be obtained by subtracting the image plane velocityof angular shake (before reduction) 302 from the output of the motionvector detector 201.

A LPF 211 receives the image plane velocity of translational shake(before reduction) 303 as an input from the translational shakeextractor 207, applies a low-pass filter, extracts a portion in aspecific frequency band, and outputs it. The frequency band of shake tobe extracted is a band of 10 Hz or less which includes the frequency ofcamera shake. However, since the dominant frequency band of shake whenperforming image shooting at slow shutter speed shifts to the lowfrequency side, the frequency band of the filter may be changedaccording to conditions such that the frequency band of 1 Hz or less ofshake is extracted.

A LPF 212 applies a low-pass filter to the angular velocity signalsoutput from the angular velocity detector 15 to extract signals in aspecific frequency band, and outputs them. The frequency band that theLPF 212 extracts is basically the same as the frequency band that theLPF 211 extracts.

A comparator 216 calculates a first image stabilization coefficient fromthe ratio between the output signals of the LPF 211 and the LPF 212, andoutputs a first image stabilization coefficient.

On the other hand, the acceleration detector 16 detects theaccelerations in the x-axis direction, the y-axis direction, and thez-axis direction of FIG. 1A, and outputs acceleration signals. A BPF 213applies a bandpass filter to the acceleration signals output from theacceleration detector 16 to extract signals in a specific frequency bandand outputs the extracted signals. An integrator 205 integrates theoutput signals of the BPF 213 to calculate the velocity signals andoutputs them. A translational shake calculator 401 calculates the imageplane velocity of translational shake by multiplying the shake signalsoutput from the integrator 205 by an image magnification (focallength/shooting distance).

A BPF 209 applies a bandpass filter to the angular velocity signalsoutput from the angular velocity detector 15 to extract signals in aspecific frequency band and output them. The frequency band of thefilter of the BPF 209 is basically the same as that of the BPF 213. AHPF 210 outputs the output signals of the BPF 209 in phase with theoutput signal of the integrator 205 by applying a high-pass filter.However, if complete integration is performed in the integrator 205, theprocessing of the HPF 210 becomes unnecessary.

A comparator 217 calculates a second image stabilization coefficientfrom the ratio between the output signals of the translational shakecalculator 401 and the BPF 210, and outputs it.

A subject information detector 214 detects and outputs the state of thesubject to be photographed by the image capturing apparatus 1000 and thestate of the image capturing apparatus 1000. The information of thesubject includes brightness of the subject, moving velocity of thesubject, contrast of the subject, pattern of the subject, movement ofthe background of the subject, movement of things other than thebackground of the subject, and so forth.

A shake information detector 215 receives the image plane velocity ofangular shake (before reduction) 302 and the image plane velocity oftranslational shake (before reduction) 303 as inputs from thetranslational shake extractor 207, and outputs them as they are.

A determination unit 218 receives an output signal indicating the stateof the subject and the state of the image capturing apparatus 1000 fromthe subject information detector 214, the image plane velocity ofangular shake (before reduction) 302 and the image plane velocity oftranslational shake (before reduction) 303 from the shake informationdetector 215, the first image stabilization coefficient from thecomparator 216, and the second image stabilization coefficient from thecomparator 217. Then, the determination unit 218 determines whether touse the first image stabilization coefficient or the second imagestabilization coefficient. The determination method by the determinationunit 218 will be described below.

Basically, the determination unit 218 makes a judgment on the premisethat the first image stabilization coefficient calculated based on thevelocity of the image plane shake from the motion vector detector 201 isused. This is because the signal detected by the motion vector detector201 has a wider measurable frequency band than the acceleration signaldetected by the acceleration detector 16. The frequency band referred tohere indicates a camera shake frequency band, which is generally 10 Hzor less.

However, there are situations in which the detection accuracy of themotion vector detector 201 drops. As the motion vector detector 201searches for a feature point from the image signal and detects itsmoving velocity, there are some cases that the feature point cannot bedetected precisely if the subject included in the image signal has arepetitive pattern, low contrast, or low brightness, which preventsaccurate detection. Further, when a completely different subject appearsin images between frames, the amount of movement of the feature pointcannot be calculated, so that accurate detection cannot be performed.Therefore, in such a case, the second image stabilization coefficientcalculated based on the acceleration signals from the accelerationdetector 16 is used.

Based on the output signals of the subject information detector 214, thedetermination unit 218 determines low subject brightness, low subjectcontrast, repeated patterns of the subject, fast moving velocity of thesubject, and fast movement of things other than the background, and inany of these cases, the determination unit 218 determines that thecurrent situation is the situation in which the detection accuracy ofthe motion vector detector 201 may drop. If the determination unit 218determines that the current situation is the situation in which thedetection accuracy of the motion vector detector 201 may drop, the firstimage stabilization coefficient is not used and the second imagestabilization coefficient is output.

The determination unit 218 also makes a judgment according to the ratiobetween the image plane velocity of angular shake (before reduction) andthe image plane velocity of translational shake (before reduction). Theimage plane velocity of translational shake (before reduction) 303 isobtained by subtracting the image plane velocity of angular shake(before reduction) 302 from the output of the motion vector detector201, as shown in FIG. 3. Therefore, if the image plane velocity oftranslational shake (before reduction) 303 is small, it may be buried inthe detection errors of the motion vector detector 201, the angularvelocity detector 15, and the image stabilization amount detector 208.Therefore, if there is a possibility that the image plane velocity oftranslational shake (before reduction) 303 may be buried in thedetection error compared to the image plane velocity of angular shake(before reduction) 302, the determination unit 218 does not select thefirst image stabilization coefficient, and outputs the second imagestabilization coefficient.

Upon comparing the image plane velocity of angular shake (beforereduction) 302 and the image plane velocity of translational shake(before reduction) 303, instead of using the detected values, anestimated value of the image plane velocity of translational shake(before reduction) 303 may be used. For example, first, an average ratiobetween the sum of the image plane velocity of angular shake (afterreduction) 301 and the image plane velocity of angular shake (beforereduction) 302, and the image plane velocity of translational shake(before reduction) 303 is obtained. Then, using the obtained ratio, theimage plane velocity of translational shake (before reduction) 303 isestimated from the obtained sum of the image plane velocity of angularshake (after reduction) 301 and the image plane velocity of angularshake (before reduction) 302. Then, the estimated image plane velocityof translational shake (before reduction) 303 is compared with the imageplane velocity of angular shake (before reduction) 302 to determinewhether or not there is a possibility that the image plane velocity oftranslational shake (before reduction) 303 is buried in the detectionerror. The average ratio between the sum of the image plane velocity ofangular shake (after reduction) 301 and the image plane velocity ofangular shake (before reduction) 302, and the image plane velocity oftranslational shake (before reduction) 303 alters depending on theshutter speeds. Therefore, the ratio is kept for each of the shutterspeeds.

Also, whether or not the subject is moving can be estimated byestimating the image plane velocity of translational shake (beforereduction) 303 from the sum of the image plane velocity of angular shake(after reduction) 301 and the image plane velocity of angular shake(before reduction) 302. If the output of the motion vector detector 201is larger than a value obtained by adding the sum of the image planevelocity of angular shake (after reduction) 301 and image plane velocityof angular shake (before reduction) 302 and the estimated image planevelocity of translational shake (before reduction) 303, the subject maybe moving. The estimation of whether or not the subject is moving iseffective if the images of the moving subject are dominant in the imagesof frames output from the image sensor 6. If the subject is moving, thedetermination unit 218 does not use the first image stabilizationcoefficient, but uses the second image stabilization coefficient. Thesecond image stabilization coefficient calculated based on theacceleration signals from the acceleration detector 16 can also be usedto check whether the value of the first image stabilization coefficientdeviates significantly except in situations where the shake due toshutter drive is large, such as during continuous shooting.

As a result of the judgment by the determination unit 218, the selectedfirst image stabilization coefficient or second image stabilizationcoefficient is integrated in an integrator 219, and is multiplied by theangular velocity signals from the angular velocity detector 15 in atranslational shake amount calculator 220, thereby converted into anamount of translational shake on the imaging surface.

Next, a flow of a calculation process of an amount of translationalshake described above will be described with reference to a flowchart ofFIG. 4.

The calculation process of an amount of translational shake shown inFIG. 4 starts when an aiming signal is input. The aiming signal isdetermined and input based on a signal from a finder (not shown), asignal from the angular velocity detector 15, and a signal from theswitch SW1. At the same time as the start of this process, the imagestabilization unit 14 and the lens actuator 13 start actuating the imagesensor 6 and the image stabilization lens 9, respectively.

In step S401, motion vector detection by the motion vector detector 201,angular velocity detection by the angular velocity detector 15,acceleration detection by the acceleration detector 16 are performed,and an image plane velocity of angular shake after reduction, which isimage stabilization information from the image stabilization amountdetector 208, is obtained.

Next, in step S402, the first image stabilization coefficient and thesecond image stabilization coefficient are calculated as described abovebased on the information obtained in step S401.

In step S403, the subject information is detected from the subjectinformation detector 214.

In step S404, the determination unit 218 determines to select the firstimage stabilization coefficient or the second image stabilizationcoefficient as described above based on the subject information obtainedin step S403 and the state related to the shake of the image capturingapparatus 1000.

In step S405, it is determined whether or not the switch SW2 is ON. Ifthe switch SW2 is OFF, the process returns to step S401. If the switchSW2 is ON, the process proceeds to step S406, and the translationalshake amount calculator 220 calculates an amount of the image planetranslational shake using the image stabilization coefficient selectedin step S404. With the start of step S406, the image stabilization unit14 and the lens actuator 13 actuates the image sensor 6 and the imagestabilization lens 9 with control amounts corresponding to an amount ofshake including the amount of translational shake. When the exposure isfinished, the process is finished.

As described above, according to the first embodiment, the translationalshake is detected by a plurality of methods, and the translational shakedetected by the method selected according to the state of the subjectand the state of the image capturing apparatus is selected, thereby itis possible to reduce the translational shake more accurately.

Second Embodiment

Next, a second embodiment of the present invention will be described.Since the configuration of the image capturing apparatus in the secondembodiment is the same as that of the image capturing apparatus 1000described with reference to FIGS. 1A, 1B, and 2, the description thereofwill be omitted here.

In a case where the accuracy of the translational image stabilization isnot very high, if the translational image stabilization is performedwhen an amount of the translational shake is small, the translationalshake may be reduced too much, and the image quality may bedeteriorated. Accordingly, in the second embodiment, a method ofpreventing deterioration of image quality by changing a gain used forobtaining a control amount for the translational image stabilizationaccording to the shooting distance and the shutter speed will bedescribed. The shooting distance referred to here is assumed to bedimensionless by dividing a shooting distance by the focal length, andis detected by the camera system control unit 5.

If it is desired to keep the shooting range constant regardless of thefocal length, this can be achieved by making the dimensionless shootingdistance have the same value. Further, in translational shake, whenconverting an amount of shake of the image capturing apparatus into avalue on the imaging surface of the image capturing apparatus, theconversion can be accomplished by dividing the amount of shake by thedimensionless shooting distance. Because of these advantages, adimensionless shooting distance is used.

The shutter speed is determined by the photographer's operation orcalculated by the photometric function of the image capturing apparatus,and is input to the shutter actuator 18 to actuate the shutter mechanism17. If the image sensor 6 has an electronic shutter function, the chargereset timing and charge read timing of the image sensor 6 may becontrolled according to the shutter speed.

The amount of angular shake does not depend on the shooting distance,whereas the amount of translational shake differs depending on theshooting distance. Further, the shorter the shooting distance is, thelarger the amount of translational shake is, and the longer the shootingdistance is, the smaller the amount of translational shake is. Further,both of the amount of angular shake and the amount of translationalshake are larger in a case where the shutter speed is slow than in acase where the shutter speed is fast. As described above, since theamount of angular shake does not change depending on the shootingdistance, the control amount need only be changed depending on theshutter speed.

On the other hand, since the amount of translational shake changesdepending on the shooting distance and the shutter speed, it isnecessary to change the control amount in consideration of the shootingdistance and the shutter speed. However, since the control amountcorresponding to the amount of translational shake differs depending onthe shooting distance, if there are a plurality of subjects and theshooting distances to the subjects are significantly different from eachother, the amount of translational shake to be reduced cannot bedetermined, so the translational image stabilization is not performed.In that case, the translational shake is reduced by a method such thatthe translational shake is reduced for each area after shooting, forexample.

Further, even in a case where the shooting distances of a plurality ofsubjects are significantly different from each other, if the AF mode ofthe image capturing apparatus is set so as to focus on the centralpoint, for example, it is presumed that the photographer has anintention to shoot a subject in that point. Therefore, the translationalimage stabilization is performed.

It is desirable to calculate the control amount for the translationalshake based on the translational shake that actually occurs duringexposure to obtain the gain, but this is not possible because the totalamount of shake during exposure is unknown until the end of exposure.Therefore, the gains with respect to the shooting distances and theshutter speeds are calculated in advance based on an average amount oftranslational shake, and are held as a table (hereinafter, referred toas “gain table”). When performing translational image stabilization,after determining the shooting distance and shutter speed, the gain fortranslational image stabilization is determined by referring to thisgain table. Since the amount of translational shake varies depending onthe posture of the photographer, the gain table may be updated accordingto the characteristics of the photographer. Further, since the amount oftranslational shake varies depending also on the posture of thephotographer, gain tables corresponding to several amounts oftranslational shake may be prepared in advance and switched betweenthem. Further, the gain tables may be switched according to the mode setby the photographer. As the mode, for example, a mode for selecting thestrength of translational image stabilization, a macro shooting mode,and the like may be considered.

Further, the amount of translational shake during exposure may beestimated based on the amount of translational shake before theexposure, and the gain table to be referred to may be switched. From thetendency of the amount of translational shake before exposure, it may bedetermined that the amount of translational shake is large or small, andthe table to be basically referred to may be updated.

Based on the amount of translational shake before exposure, the amountof translational shake during exposure that takes into account theshutter speed and shooting distance may be estimated, and the gain valuemay be calculated by comparing the estimated amount of translationalshake with a predetermined reference amount of shake.

Here, the features of the table made from the shutter speed and theshooting distance will be described with reference to FIG. 5.

In FIG. 5, the horizontal axis represents the shooting distance and thevertical axis represents the shutter speed. A hatched region 501 is aregion where the amount of shake is larger than the predeterminedreference amount of shake, that is, a region where translational shakeshould be reduced. Even in the region 501, the amount of translationalshake varies, and the amount of translational shake is larger in theregion where the shooting distance is shorter and the shutter speed isslower. Therefore, the gain is increased in the part of the region 501where the amount of translational shake is large.

On the other hand, a white region 502 is a region in which the amount oftranslational shake is equal to or less than the predetermined referenceamount of shake. This region 502 is a region in which the translationalimage stabilization is not always necessary. However, since the amountof translational shake is included to some extent especially in thevicinity of the boundary between the region 501 and the region 502, thetranslational image stabilization may be performed in the vicinity ofthe boundary, and the gain may be determined according to the detectionaccuracy of the translational shake. For example, a higher gain may beset in a part of the region 502 close to the region 501, and a lowergain may be set in an other part of the region 501.

As described above, in a case where the detection accuracy of thetranslational shake is high, by putting a large gain value even for aregion where the translational image stabilization is not essential, theeffect of the translational image stabilization can be maximized.

The gain value may be set in any way. For example, 1 is set in theregion where the translational image stabilization is essential, and avalue close to 0 is set in the region where the translational imagestabilization is not essential. When executing the translational imagestabilization, the control amount for the detected translational shakeis multiplied by the gain value.

Next, a flow of a calculation process of an amount of translationalshake in the second embodiment will be described with reference to aflowchart of FIG. 6. The process shown in FIG. 6 starts when the powerof the image capturing apparatus is turned ON or when the switch SW1 isturned on.

The shooting distance is detected in step S501, and a set value of theshutter speed is confirmed in step S502. In step S503, the gain table isreferred to according to the characteristics of the photographer, theshooting mode, and the like, and in step S504, the gain value isdetermined according to the shooting distance and the shutter speed.After that, the processes of steps S401 to S404 of FIG. 4 are performedto select the correction coefficient, but detailed description thereofwill be omitted here.

It is determined in step S405 whether or not the switch SW2 is turnedon, and if it is turned on, the translational image stabilization isperformed using the gain value determined in step S504 and the imagestabilization coefficient selected in step S404. If it is determinedthat the switch SW2 is OFF in step S405, the process returns to stepS501 again to determine a new gain value.

As described above, according to the second embodiment, in addition tothe effects of the first embodiment, deterioration of image quality canbe further suppressed.

Also in the second embodiment, the first image stabilization coefficientis obtained based on the motion vector detected by the motion vectordetector 201 and the second image stabilization coefficient is obtainedbased on the acceleration detected by the acceleration detector 16according to the configuration shown in FIG. 2, and one of them isselected and the gain is applied. However, the present invention is notlimited to this, and the method for obtaining the amount oftranslational shake is not particularly limited. For example, the secondembodiment may be applied to an image capturing apparatus having aconfiguration capable of obtaining only one of the first imagestabilization coefficients and the second image stabilizationcoefficients described in the first embodiment. In addition, a method ofsecond-order integration of acceleration detected by an accelerationsensor, an inertial navigation method, or the like can also be used.

Third Embodiment

Next, a third embodiment of the present invention will be described.

In the first embodiment described above, the method of calculating thefirst image stabilization coefficient using the motion vector detector201 and the angular velocity detector 15 has been described. However, ina case where the motion vector detector 201 cannot detect the motionvector, in a case where the photographer is not firmly holding the imagecapturing apparatus, or in a case where the photographer is panning theimage capturing apparatus, an error will affect the calculation of theamount of translational shake, and obtained result may be unstable.

In the third embodiment, a method of calculating the first imagestabilization coefficient will be described in a case where the motionvector detector 201 cannot detect the motion vector, in a case where thephotographer is not firmly holding the image capturing apparatus, or ina case where the photographer is panning the image capturing apparatus.

The comparator 216 compares the output of the LPF 211 with the output ofthe LPF 212. In the first embodiment, the method of performingcalculation using all the outputs of the LPF 211 and the LPF 212 hasbeen described. On the other hand, in the third embodiment, acalculation method in a case where a situation in which the data cannotbe acquired as described above may occur will be described withreference to FIG. 7. The constituents in FIG. 7 same as those in FIG. 2are assigned the same reference numbers, and the description thereofwill be omitted.

In the third embodiment, the outputs of the LPF 211 and the LPF 212 areinput to a data determination unit 703. The data determination unit 703determines whether at least one of the cases where the detectionaccuracy of the motion vector detector 201 is low, the motion vectordetector 201 cannot detect the motion vector, the photographer is notfirmly holding the image capturing apparatus, and the photographer ispanning the image capturing apparatus occurs. If any of the above casesoccurs, the data determination unit 703 outputs a flag together with thesignals of the LPF 211 and the LPF 212, and outputs the signals of theLPF 211 and the LPF 212 otherwise.

A data storage 704 stores the output of the data determination unit 703as time-series data including the flag. The comparator 216 calculatesthe first image stabilization coefficient from the ratio between theoutput signals of the LPF 211 and LPF 212 output from the data storage704. At this time, the comparator 216 inputs the output signals of theLPF 211 and LPF 212, corresponding to the total number of data includingdata with a flag and data without a flag obtained during the period oftime corresponding to the shutter speed. Then, the first imagestabilization coefficient is calculated using only the data without aflag. This is because the image stabilization effect is higher when thefirst image stabilization coefficient is calculated using the dataobtained during the period of time corresponding to the shutter speed.However, depending on the data sampling cycle, the number of data willbe small when the shutter speed is fast. In such a case, the first imagestabilization coefficient is calculated using the data obtained in alonger period of time than a period of time corresponding to the shutterspeed.

The output signal from the data storage 704 is input to a reliabilitycalculator 707, and the reliability of the first image stabilizationcoefficient calculated by the comparator 216 is calculated. Thereliability is obtained by comparing the maximum number of data that canbe used to calculate the first image stabilization coefficient with thenumber of data that can be used to calculate the current first imagestabilization coefficient. For example, if the number of data that canbe used to calculate the first image stabilization coefficient isreduced to half or less, the reliability of the first imagestabilization coefficient becomes considerably low, so the first imagestabilization coefficient calculated in the past is also used for thefinal calculation of the first image stabilization coefficient. Further,for example, the reliability may be obtained from the number of datathat can be used currently with respect to the number of data with whicha first image stabilization coefficient can be obtained stably. That is,the reliability is not limited to those described above as long as it ispossible to calculate whether or not the number of data that can be usedfor the calculation of the current correction coefficient is reliable,and the calculation method thereof is not limited.

The output signal of the data storage 704, the first image stabilizationcoefficient calculated by the comparator 216, and the reliabilitycalculated by the reliability calculator 707 are input to an imagestabilization coefficient storage 705. Then, if a flag is set to theimmediately previous data with respect to the latest data, no flag isset to the latest data, and the reliability calculated by thereliability calculator 707 is equal to or higher than a certain value,the first image stabilization coefficient is stored.

A stored image stabilization coefficient reliability calculator 706updates the reliability of the first image stabilization coefficientstored in the image stabilization coefficient storage 705. This isbecause the reliability of the first image stabilization coefficientstored in the image stabilization coefficient storage 705 is consideredto decrease over time. Therefore, the stored image stabilizationcoefficient reliability calculator 706 measures the elapsed time fromthe time at which the first image stabilization coefficient is stored inthe image stabilization coefficient storage 705, and performs acalculation to lower the reliability according to the elapsed time. Thecalculation of the reliability coefficient performed at this time may bea linear calculation or a non-linear calculation.

An image stabilization coefficient calculator 708 calculates the finalfirst image stabilization coefficient from the outputs of thereliability calculator 707, the comparator 216, the image stabilizationcoefficient storage 705, and the storage correction coefficientreliability calculator 706. Specifically, the image stabilizationcoefficient calculator 708 outputs the first image stabilizationcoefficient output from the comparator 216 as the final first imagestabilization coefficient if the reliability output from the reliabilitycalculator 707 is equal to or higher than a certain threshold value. Onthe other hand, if the reliability output from the reliabilitycalculator 707 is lower than the certain threshold value and thereliability output from the stored image stabilization coefficientreliability calculator 706 is equal to or higher than the certainthreshold value, then the first image stabilization coefficient outputfrom the comparator 216 and the first image stabilization coefficientstored in the image stabilization coefficient storage 705 are weightedand averaged according to their reliabilities, and the result isoutputted as the final first image stabilization coefficient. If thereliability output from the reliability calculator 707 is lower than thecertain threshold value and the reliability output from the storagecorrection coefficient reliability calculator 706 is also lower than thecertain threshold value, 0 is output as the first image stabilizationcoefficient.

After that, the determination unit 218 determines whether to use thefirst image stabilization coefficient or the second image stabilizationcoefficient in the manner as described in the first embodiment.

Next, the flow of processing performed by the image stabilizationcoefficient calculator 708 in the third embodiment will be describedwith reference to a flowchart of FIG. 8. This processing is performed asarithmetic processes of the first image stabilization coefficientperformed in step S402 of FIG. 4.

In step S601, the data determination unit 703 determines whether atleast one of the conditions that the detection accuracy of the motionvector detector 201 is low, the motion vector detector 201 cannot detectthe motion vector, the photographer is not firmly holding the imagecapturing apparatus, and the photographer is panning the image capturingapparatus is met.

Then, in step S602, if it is determined in step S601 that any of theconditions is met, the data storage 704 stores the flag together withthe output signals of the LPF 211 and the LPF 212. If none of theconditions is met, the output signals of LPF 211 and LPF 212 are saved.

In step S603, the comparator 216 calculates the first imagestabilization coefficient from the output signals, with no flag, of theLPF 211 and the LPF 212.

In step S604, the reliability calculator 707 calculates the reliabilityof the first image stabilization coefficient calculated by thecomparator 216.

Next, in step S605, the image stabilization coefficient storage 705determines whether or not a flag is set to the immediately previous datafrom the latest data, no flag is set to the latest data, and thereliability obtained by the reliability calculator 707 is equal to orgreater than a certain value. If the above conditions are met, theprocess proceeds to step S608, and if not, the process proceeds to stepS606.

In step S608, the image stabilization coefficient storage 705 stores thefirst image stabilization coefficient and proceeds to step S609. In stepS609, the reliability is adjusted according to the passage of time inthe stored image stabilization coefficient reliability calculator 706.

In step S606, the image stabilization coefficient calculator 708determines whether the reliability is equal to or greater than thethreshold value. If the reliability is equal to or greater than thethreshold value, the process proceeds to step S607, and the first imagestabilization coefficient calculated in step S603 is used as the finalfirst image stabilization coefficient.

On the other hand, if the reliability is less than the threshold value,the process proceeds to step S610, and the image stabilizationcoefficient calculator 708 determines whether or not the reliabilityadjusted in step S609 is equal to or greater than a threshold value. Ifthe adjusted reliability is equal to or greater than the thresholdvalue, the process proceeds to step S611, and the first imagestabilization coefficient obtained in step S603 and the first imagestabilization coefficient stored in the image stabilization coefficientstorage 705 in step S608 are weighted and averaged based on theirrespective reliabilities to calculate the final first imagestabilization coefficient.

If the adjusted reliability is less than the threshold value in stepS610, the process proceeds to step S612, and the final first imagestabilization coefficient is set to 0. Here, 0 may be used so that thecorrection is not performed, or a signal indicating that the imagestabilization cannot be performed by this method may be output.

When the first image stabilization coefficient is determined, theprocess ends.

As described above, according to the third embodiment, in addition tothe effect of the first embodiment, it is possible to further suppressthe detection error of the translational shake based on the motionvector.

OTHER EMBODIMENTS

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2021-017743, filed Feb. 5, 2021 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image stabilization apparatus comprising atleast one processor and/or circuitry which functions as: a motion vectordetector that detects a motion vector from images repeatedly output froman image sensor; a first calculator that calculates a first imagestabilization coefficient to be used for calculating an amount oftranslational shake based on the motion vector; a second calculator thatcalculates a second image stabilization coefficient to be used forcalculating an amount of translational shake based on acceleration ofshake of an image capturing apparatus; a determination unit that selectseither of the first image stabilization coefficient or the second imagestabilization coefficient based on information about accuracy ofdetection of the motion vector by the motion vector detector; and atranslational shake calculator that calculates an amount oftranslational shake using the first image stabilization coefficient orthe second image stabilization coefficient selected by the determinationunit, wherein, in a case where the information indicates that theaccuracy is low, the determination unit selects the second imagestabilization coefficient, and select the first image stabilizationcoefficient otherwise.
 2. The image stabilization apparatus according toclaim 1, wherein the information includes information on whether or notany of the images include a repetitive pattern, contrast of the images,brightness of the images, movement of a subject in the images, and stateof background of the images, and the determination unit determines thatthe accuracy is low if the information indicates any of states that anyof the images includes a repetitive pattern, the contrast is lower thana predetermined contrast, the brightness is lower than a predeterminedbrightness, the movement of the subject is larger than a predeterminedmovement, movement of the background is larger than a predeterminedmovement.
 3. The image stabilization apparatus according to claim 1,wherein the determination unit determines that the accuracy is low if aratio of image plane velocity of translational shake on an imaging planeof the image sensor calculated in the past based on the motion vectorused for calculating the first image stabilization coefficient to imageplane velocity of angular shake on the imaging plane of the image sensorcalculated based on angular velocity of shake of the image capturingapparatus is lower than a predetermined ratio.
 4. The imagestabilization apparatus according to claim 1, wherein the determinationunit estimates image plane velocity of translational shake on an imagingplane of the image sensor from image plane velocity of angular shake onthe imaging plane of the image sensor calculated based on newly detectedangular velocity, based on a ratio between image plane velocity ofangular shake calculated in the past based on angular velocity of shakeof the image capturing apparatus and image plane velocity oftranslational shake calculated in the past based on the motion vectorfor calculating the first image stabilization coefficient, and thedetermination unit determines that the accuracy is low if a ratio of theestimated image plane velocity of translational shake to the image planevelocity of angular shake used for the estimation is lower than apredetermined ratio.
 5. The image stabilization apparatus according toclaim 1, further comprising at least one processor and/or circuitrywhich functions as a gain unit that determines a gain based on a shutterspeed at a time of shooting an image and a shooting distance, andapplies the gain to the first image stabilization coefficient or thesecond image stabilization coefficient selected by the determinationunit, wherein the translational shake calculator calculates the amountof translational shake using the gained first image stabilizationcoefficient or the gained second image stabilization coefficient.
 6. Theimage stabilization apparatus according to claim 5, wherein the gainunit makes the gain larger in a case where the shutter speed is a firstshutter speed than in a case where the shutter speed is a second shutterspeed which is faster than the first shutter speed.
 7. The imagestabilization apparatus according to claim 5, wherein the gain unitmakes the gain larger in a case where the shooting distance is a firstshooting distance than in a case where the shooting distance is a secondshooting distance which is longer than the first shooting distance. 8.The image stabilization apparatus according to claim 5, furthercomprising a gain table that stores gains corresponding to a pluralityof different shutter speeds and a plurality of different shootingdistances, wherein the gain unit determines the gain by referring to thegain table.
 9. The image stabilization apparatus according to claim 8,further comprising a plurality of the gain tables corresponding to modesof the image capturing apparatus and characteristics of photographers,wherein, among the plurality of gain tables, the gain unit refers to again table corresponding to a mode of the image capturing apparatus andcharacteristics of a photographer.
 10. The image stabilization apparatusaccording to claim 1, further comprising at least one processor and/orcircuitry which functions as: a reliability calculator that calculatesreliability of the first image stabilization coefficient; a storage thatholds the first image stabilization coefficient and the reliability ofthe first image stabilization coefficient; an adjustor that adjusts thereliability stored in the storage according to passage of time since thereliability is stored; and a third calculator that calculates the firstimage stabilization coefficient to be input to the determination unitout of the first image stabilization coefficient newly calculated by thefirst calculator and the first image stabilization coefficient stored inthe storage based on reliability of the newly found first imagestabilization coefficient and the reliability adjusted by the adjustor.11. The image stabilization apparatus according to claim 10, wherein thethird calculator selects the newly found first image stabilizationcoefficient if the reliability of the newly found first imagestabilization coefficient is equal to or greater than a first threshold,weights and averages the newly found first image stabilizationcoefficient and the stored first image stabilization coefficient basedon the reliability of the newly found first image stabilizationcoefficient and the adjusted reliability if the reliability of the newlyfound first image stabilization coefficient is less than a thirdthreshold and if the adjusted reliability is equal to or greater than asecond threshold, and does not output the first image stabilizationcoefficient if the reliability of the newly found first imagestabilization coefficient is less than the third threshold and if theadjusted reliability is less than the second threshold.
 12. The imagestabilization apparatus according to claim 10, wherein the adjustorreduces the reliability according to passage of time since thereliability is stored in the storage.
 13. The image stabilizationapparatus according to claim 10, wherein the first calculator calculatesthe first image stabilization coefficient based on a plurality of motionvectors output during a period corresponding to the shutter speed exceptfor a motion vector whose detection accuracy is indicated as low in theinformation.
 14. The image stabilization apparatus according to claim10, wherein, in a case where the shutter speed is faster than apredetermined shutter speed, the first calculator calculates the firstimage stabilization coefficient based on a plurality of motion vectorsoutput during a period longer than a period corresponding to the shutterspeed except for a motion vector whose detection accuracy is indicatedas low in the information.
 15. The image stabilization apparatusaccording to claim 1, further comprising at least one processor and/orcircuitry which functions as an angular velocity detector that detectsan angular velocity, wherein the translational shake calculatorcalculates the amount of translational shake based on the first imagestabilization coefficient or the second image stabilization coefficientselected by the determination unit and the angular velocity detected bythe angular velocity detector.
 16. An image stabilization apparatuscomprising at least one processor and/or circuitry which functions as: afirst calculator that calculates an image stabilization coefficient tobe used for calculating an amount of translational shake based on amotion vector obtained from images repeatedly output from an imagesensor; a gain unit that determines a gain based on a shutter speed at atime of shooting an image and a shooting distance; and a secondcalculator that calculates an amount of translational shake using thegain determined by the gain unit and the image stabilization coefficientcalculated by the first calculator, wherein the gain unit makes the gainlarger in a case where the shutter speed is a first shutter speed thanin a case where the shutter speed is a second shutter speed which isfaster than the first shutter speed, and wherein the gain unit makes thegain larger in a case where the shooting distance is a first shootingdistance than in a case where the shooting distance is a second shootingdistance which is longer than the first shooting distance.
 17. The imagestabilization apparatus according to claim 16, further comprising atleast one processor and/or circuitry which functions as an angularvelocity detector that detects an angular velocity, wherein the secondcalculator calculates the amount of translational shake based on theimage stabilization coefficient and the angular velocity detected by theangular velocity detector.
 18. An image capturing apparatus comprising:an image sensor; and an image stabilization apparatus that comprises atleast one processor and/or circuitry which functions as: a motion vectordetector that detects a motion vector from images repeatedly output fromthe image sensor; a first calculator that calculates a first imagestabilization coefficient to be used for calculating an amount oftranslational shake based on the motion vector; a second calculator thatcalculates a second image stabilization coefficient to be used forcalculating an amount of translational shake based on acceleration ofshake of an image capturing apparatus; a determination unit that selectseither of the first image stabilization coefficient or the second imagestabilization coefficient based on information about accuracy ofdetection of the motion vector by the motion vector detector; and atranslational shake calculator that calculates an amount oftranslational shake using the first image stabilization coefficient orthe second image stabilization coefficient selected by the determinationunit, wherein, in a case where the information indicates that theaccuracy is low, the determination unit selects the second imagestabilization coefficient, and selects the first image stabilizationcoefficient otherwise.
 19. An image capturing apparatus comprising: animage sensor; and an image stabilization apparatus that comprises atleast one processor and/or circuitry which functions as: a firstcalculator that calculates an image stabilization coefficient to be usedfor calculating an amount of translational shake based on a motionvector obtained from images repeatedly output from an image sensor; again unit that determines a gain based on a shutter speed at a time ofshooting an image and a shooting distance; and a second calculator thatcalculates an amount of translational shake using the gain determined bythe gain unit and the image stabilization coefficient found by the firstcalculator, wherein the gain unit makes the gain larger in a case wherethe shutter speed is a first shutter speed than in a case where theshutter speed is a second shutter speed which is faster than the firstshutter speed, and wherein the gain unit makes the gain larger in a casewhere the shooting distance is a first shooting distance than in a casewhere the shooting distance is a second shooting distance which islonger than the first shooting distance.
 20. An image stabilizationmethod comprising: detecting a motion vector from images repeatedlyoutput from an image sensor; calculating a first image stabilizationcoefficient to be used for calculating an amount of translational shakebased on the motion vector; calculating a second image stabilizationcoefficient to be used for calculating an amount of translational shakebased on acceleration of shake of an image capturing apparatus;selecting either of the first image stabilization coefficient or thesecond image stabilization coefficient based on information aboutaccuracy of detection of the motion vector; and calculating an amount oftranslational shake using selected one of the first image stabilizationcoefficient or the second image stabilization coefficient, wherein, thesecond image stabilization coefficient is selected in a case where theinformation indicates that the accuracy is low, and the first imagestabilization coefficient is selected otherwise.
 21. An imagestabilization method comprising: calculating an image stabilizationcoefficient to be used for calculating an amount of translational shakebased on a motion vector obtained from images repeatedly output from animage sensor; determining a gain based on a shutter speed at a time ofshooting an image and a shooting distance; and calculating an amount oftranslational shake using the gain and the image stabilizationcoefficient, wherein the gain is made larger in a case where the shutterspeed is a first shutter speed than in a case where the shutter speed isa second shutter speed which is faster than the first shutter speed, andwherein the gain is made larger in a case where the shooting distance isa first shooting distance than in a case where the shooting distance isa second shooting distance which is longer than the first shootingdistance.